1. Field of the Invention
The present invention relates to a method and apparatus for sealing a liquid crystal display element cell and, more particularly, to a method and apparatus for sealing a liquid crystal display element cell which uses Z-rings as seal rings for forming pressure regions that press the liquid crystal display element cell.
2. Description of the Prior Art
A liquid crystal display element cell is formed by forming an aligning film on a thin film transistor substrate (to be referred to as a TFT substrate hereinafter), applying a thermosetting adhesive also serving as a spacer around the display region of the aligning film surface by printing or the like, placing a color filter substrate (to be referred to as a CF substrate hereinafter) on the TFT substrate through the thermosetting adhesive, and adhering the TFT substrate and the CF substrate by calcining the thermosetting adhesive through heating and pressing. A liquid crystal is sealed in the liquid crystal display element cell.
When applying the thermosetting adhesive around the display region in order to seal the liquid crystal, a gap (called an opening) is formed in the thermosetting adhesive. The liquid crystal is sealed in the liquid crystal display element cell in the following manner. The liquid crystal display element cell is placed into a vacuum atmosphere. The opening is brought into contact with the liquid crystal placed in a liquid crystal plate or the like. Then, the atmosphere is restored to the atmospheric pressure, so that the liquid crystal is injected into the air gap of the liquid crystal display element cell due to the atmospheric pressure difference.
The air gap into which the liquid crystal has been injected has expanded to be larger than the gap formed by the spacer during calcining, and gap variations occur within the plane of the surface. For this reason, before sealing the opening with the ultraviolet-curing resin, the liquid crystal display element cell into which the liquid crystal has been injected is pressed from the front and lower surfaces to make the gap uniform.
When the liquid crystal display element cell is pressed by bringing a resin plate or air cushion into contact with it, the liquid crystal display element cell may crack due to foreign matter or the like sandwiched between the resin plate or air cushion and the liquid crystal display element cell, or the liquid crystal display element cell may not be uniformly pressed due to variations in size precision of the resin plate to cause a gap defect. Therefore, pressing is performed with a pneumatic pressure (Japanese Unexamined Patent Publication No. 7-5405 and the like).
FIG. 1 shows an example of a gap adjustment unit that employs pneumatic pressing.
FIG. 1 shows a liquid crystal panel adhering unit that employs pneumatic pressing. In an adhering unit 50, a structure obtained by setting first and second substrates 4 and 6 for forming a display panel to oppose each other through a seal member 54, and adhering them by calcination is placed in a pressure chamber 56. The peripheral portion of the substrate structure is sealed from above and below it through vacuum packing seal rings 60. Pressurized air from a pressurized air supply source 52 is supplied into sealed spaces, which are defined by the seal rings 60, the substrate structure, and partition plates 66 and 68 to form the pressure chamber 56 and a pressure chamber 57. The pressures in the pressure chambers 56 and 57 increase accordingly to form a bonded substrate structure.
A sealing apparatus which performs gap adjustment of a liquid crystal display element cell with pneumatic pressing using seal rings is described in Japanese Unexamined Patent Publication Nos. 4-147217, 5-34653, 6-235896, and the like.
The first problem of the prior art described above is as follows. When gap adjustment between the substrates is performed before injection of the liquid crystal, expansion of the liquid crystal panel that takes place during injection of the liquid crystal cannot be avoided. The second problem is as follows. To hermetically seal the pressure chambers, ordinary O-rings are used. In an O-ring having a circular section, the contact width of the contact portion between an O-ring 60 and a partition plate 66 is small, as shown in FIG. 2. When a pressurized gas is introduced into the sealed space, the gas leaks from the contact portion of the O-ring 60, and the substrate display surface cannot be uniformly pressed.
U-shaped seal rings 62 and 64 are also known, as shown in FIGS. 3 and 4. Although the length of a contact portion c or d through which the seal ring 62 or 64 is in contact with a partition plate 66 or 68 is large, the bonding pressure of the contact portion c or d does not increase sufficiently, and gas leakage may sometimes occur.